The purpose was to isolate a nuclease which can hydrolyze phosphodiester bonds at particular residues in RNA and would therefore be useful in determining the primary sequence of various types of ribonucleic acid. Also, it is of interest to examine the interaction of the nucleases with the polyamines since these agents have been found in elevated levels in the serum and urine of cancer patients. Spermidine previously had been shown to bind to and effect the activity of the Citrobacter nuclease. The effects of the polyamines on polynucleotide inhibition of ribonuclease activity was also explored. Two enzymes were of primary importance in these studies: the Enterobacter nuclease and the Staphylococcal nuclease.